Online ad network Federated Media, which serves Web sites like VentureBeat and hundreds of others with ads it gets from large companies, is close to raising a $30 million round at a $200 million pre-money valuation, according to a well-placed source.

In January, news leaked that the company had hired a small bank, GCA Savvian, and was trying to raise up to $50 million at a $125 million valuation, after having rejected a $100 million buyout offer.

Then, in early March, other leaks suggested that Sausilito, Calif.-based Federated Media was trying to raise between $20 and $30 million, while entertaining various offers and aiming for a substantially higher valuation.

The company is like many other startups that have grown large over the past several years — aiming for large amounts of funding at nine-digit valuations despite the larger questions about the stability of the national economy. The company may be getting while the getting still is good. After all, social network Bebo managed to sell itself to AOL for $850 million last week.

But we and others have been wondering if the window of fundraising opportunity is closing. [Update: In fact, Valleywag reports the deal may not be as far advance as we’ve heard.] We reported on Monday that fast-growing IM aggregator company Meebo is looking to raise a round valuing it at up to $250 million. Widget company Slide raised $50 million at a $550 valuation last December — a deal they rushed to finish before the economy got worse this past year. Social news site Digg put itself up for sale last fall, as well, hoping to sell for $300 million — it may be looking at a smaller amount, now, and hasn’t yet sold.

Of course, while companies like Bebo, Meebo, Slide, and Digg have yet to figure out significant revenue models, Federated Media has. It takes 40 percent revenue from the sites that run its ads — and those sites are making some good money. It has previously raised $7.5 million in two rounds from Panorama Capital, a group formerly part of JP Morgan Partners, The New York Times and the Omidyar Network. For this round, we and our source suspect that the investors will be larger private equity firms and hedge funds.

A larger question for Federated Media: How will it continue to maintain its large, influential base of publishers — while taking a 40 percent revenue cut — even as at least some of those publishers are considering joining forces on their own?